A Combined use of Hydraulic and Hydrological Model to Characterise Channel Hydro-Geomorphology of a Tropical River Basin of West Bengal, India

Abstract The present research work is intended to portray the changing nature of channel hydro-geomorphological properties from upstream to downstream of the Mayurakshi River located in a plateau fringe region of Jharkhand and West Bengal. An intensive field investigation has been done on 14 different cross-sectional sites to measure some important geomorphic parameters like channel depth, width, bank height, hydraulic radius, wetted perimeter, etc. during the post monsoon season of 2021. For more accurate locational information, a Post Processed Kinematic Survey (PPK) using Differential Global Positioning System (DGPS) survey and a Current Meter instrument have been done to measure the river bed profile and channel velocity respectively. The objective of this paper is to compare the field observed discharge data with selected hydraulic and hydrological models and to determine the scientifically accepted and cost-effective way of estimating lean period flow amount within a section of a tropical river like the Mayurakshi River. Here, Manning’s equation and Kinematic Wave Parameter (KWP) - two important geomorphic-based methods have been executed for computing the discharge amount, where the study reveals Hydraulic method of Manning’s equation provide better result in discharge estimation compared to the hydrological method. Moreover, the role fragmented nature of the flow pattern, human intervention in active river bed areas by continuous sand mining activity and installation of dams and barrages restrict the free flow of the river causing inadequate discharge and higher channel in-efficiency throughout the studied reach.